True Position

[[AG...]]

Just curious about how anyone would set this up? I am in discussion with the engineer as in he believes that this part is in tolerance as i am getting OOT. I have been discussing this for a day and a half and i might be confusing myself, running in circles? I am setting it up as shown with alignment as A datum, all dims come from the A datum plane in the X axis. The B datum, all dims come from the B datum in the Y axis. In the two separate alignments i have for these i am using the A datum in the X and the Top plane as my Z. The same thing for the B datum alignment, i am using the Y for my B and the Top plane as my Z. When i use Best Fit alignment, i am reporting a good part, i explained how Best fit works and he is not sure of it. In my past endeavor's i used Best fit for a hole pattern like this all day, no issues. I see this as a Best Fit scenario, am i incorrect? Just because the hole pattern is of course the important part. Thank you in advance for any direction or if i am just overthinking this scenario.

  

[[Ma...]]

If A is in -X vector, then report TP|A only X and for TP|B only Y ( or Z i don't know )

[[Jo...]]

The GDT is only asking you to check the Orientation of the bores to the datum planes

 

[[Ka...]]

O.K. Lets try:
Reference A is the left side of the body in your drawing.
Reference B is unclear. On the one hand, it could be formed from the sides of the body (Bx) or from two holes B1 an B2 define (By). 
The Position tolerance definition match not the norm DIN EN ISO 1101.

In the position tolerance 0.3 to A, no further degree of freedom is restricted. And no CZ is specified either. This means that each hole is toleranced individually. It is NOT a drilling pattern.
The same applies to tolerance 0.3 for B, although in this case there is the additional issue that ‘B’ is not clearly defined.
 

Regards
Karsten

 

[[Ch...]]

When using best fit of bore pattern; Use 'View Tolerance' under Best Fit Method if you want it to match results you would get using a functional gage. 

 

See my post about view tolerance here:

 

Edited March 9

[[DW...]]

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 I have heard a best fit alignment described by imagining you are wiggling the feature(s) around on the part until the deviation between nominal and actual is the smallest. So a best fit alignment answers how well the overall part geometry matches the CAD, where a datum alignment answers will this part assemble and function correctly. 

I would also tend to agree with

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 assessment on orientation given the holes are being checked with respect to a single plane. Overall, this drawing seems to be lacking in controlling the hole positions effectively, especially since it has 3 mutually perpendicular planes to set up a solid DRF. 

[[Ja...]]

An engineer disagrees with the part being out of spec? I've never had that happen before. Do I need to add " I'm joking" ?

[[AG...]]

Thank you all for the help here on my topic. It is very much appreciated for sure. I have explained how Best Fit works the way that i was taught and understand it. I too explain it as taking all the features and the movement of all is the deviation between the nominal and actual at the smallest. I also explain it as all the features move to try to fit within the position tolerance. There could be one feature using more than another feature and that it would use that to move closer to the position called for. Thank you for the explanation on the 'View Tolerance' Best fit method for functional gage. I won't use this too often but definitely for the future. All of the responses were great, this is why i am constantly on the forum, learning all the time. So, the final verdict on the program and TP callouts. I used Datum -A- callout as a Line on the side face per the customer on how they set it up in the X axis and Datum -B- is a 2D Line from left to right. The alignment used were only reporting -A- in the X and -B- in the Y. They used circles instead of cylinders like i used the first time and i used a plane for Datum -A-. The outcome they were satisfied and engineer too.